Method for creating spiral swath patterns for convex polygon shaped field boundaries

ABSTRACT

A computationally efficient method for generating a spiral swath pattern for a region of a field bounded by a convex polygon, the method automatically generating curved portions for the swath pattern having radii of curvature greater than a minimum turning radius based on the minimum turning radius and a definition of the field boundary.

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 11/681,445 filed Mar. 2, 2007, which application is hereinincorporated by reference.

TECHNICAL FIELD

The present invention relates generally to swath pattern generationmethods for work vehicles, and more particularly to a computationallyefficient method for generating spiral swath patterns for a region of afield bounded by a convex polygon, the method automatically generatingcurved portions of the swath pattern having radii of curvature greaterthan or equal to a minimum turning radius based on the minimum turningradius and a definition of the field boundary.

BACKGROUND ART

Off road work vehicles in the agricultural, mining and constructionfields, such as tractors, and the like, have traditionally operated withmanual steering. Improvements in control system design and relatedposition sensing technology, such as global positioning systems (GPS),including differential correction systems, as well as real timekinematic (RTK) satellite navigation have led to an increase in the useof automatic guidance control systems for these vehicles. Thecombination of improved navigation input signals precisely identifyingvehicle position and speed with sophisticated on board vehicleelectronic control systems allows for automatic guidance systems capableof steering the vehicle with a high degree of accuracy when traversingterrain.

To provide this control, the prior art teaches using satellitepositioning information by an onboard vehicle navigation control systemto accurately determine and control a vehicle's position while operatingin a field. A preplanned route, based on information previously knownabout the terrain of the field, or a control system generated route maybe used. The control methods are well known in the art, and may involvemultiple position transmitters or receivers, with various signals usedto derive vehicle location, elevation, direction of travel or heading,and speed.

The task of precision guidance of an agricultural vehicle involves notonly accurately determining vehicle position in a field, but alsodefining an efficient swath pattern or array of swath lines to befollowed by the vehicle that will, in conjunction with the swath widthof an element associated with the vehicle, create an overall swathpattern that efficiently and effectively covers the crop area of afield. The pattern must be located and oriented on the field, and thephysical characteristics and limitations of the vehicle and coupledimplement must be identified and provided to the navigation system.Implement or header width, location of the implement or header withrespect to the vehicle, and limitations on the vehicle and associatedimplement movement, such as minimum turning radius, must also beconsidered. With this information it is possible to define an array orseries of swath lines for the vehicle to travel in an attempt to coverall cultivatable portions of a field without unnecessary skips oroverlaps.

Calculating the series of swath lines needed to cover an area withoutsubstantial skips or overlaps is relatively straightforward whenstraight lines can be used; however, not all fields can be covered inthis manner. In some fields it may be desirable to use a spiral swathpattern in which the swath lines require a variation in curvature alongat least some portion of its length. Such conditions preclude a completereliance on geometrically predefined swath lines, such as straight linesor constant radius curves. In order to provide generally equally spacedswath lines for a spiral swath pattern, each adjacent swath line mustchange slightly compared to the prior swath line as the vehicletraverses field.

Vehicle navigation systems typically must be able to store and retrieveswath path information as well as determine new adjacent swath pathsfrom a baseline swath path or create new swath paths from definedstarting and ending positions. The number of swath lines to be storedand/or determined increases as the size of the field increases.Presently known systems for generating spiral swath patterns require asignificant number of positional data points to fully define the swathlines between starting and ending points compared to using only startingand ending position points to create straight-line paths. Thecomputation time and memory storage required for generating andtraversing a spiral swath pattern are often drawbacks to these systems.Thus the size and arrangement of some fields is such that generatingand/or storing a spiral swath pattern according to presently knownmethods is both inconvenient and inefficient because of the computationtime and memory requirements, especially if the field is large and thesystem boundary is known and can be described by a convex polygon.

In addition, presently known systems typically generate swath lines as afunction of a baseline swath line. The radius of curvature of everycurved portion of each of the generated swath lines must then becomputed and compared to the minimum turning radius of the vehicle. Ifthe radius of curvature of the generated swath line is too small, thegenerated swath line must be regenerated for use by the vehicle. Oftenthis computation and regeneration is made during operation of thevehicle in the field resulting in increased computation and memoryrequirements.

What is sought is a system and method to generate spiral swath patternsfor a convex polygon shaped field which overcomes at least one of theproblems, shortcomings, or disadvantages set forth above.

SUMMARY OF THE INVENTION

What is disclosed is a method to generate spiral swath patterns for aconvex polygon shaped field which overcomes at least one of theproblems, shortcomings, or disadvantages set forth above.

According to a preferred embodiment of the present invention a methodfor generating a spiral swath pattern to be driven by a work vehicleover a convex polygon shaped region of a field is disclosed. The methodincludes determining a minimum turning radius, such that the minimumturning radius defines the minimum radius of curvature of the swathpattern and defining a swath width as a function of a lateral extent ofthe work vehicle or an implement of the work vehicle. The boundary ofthe region is defined including first through nth line segments havingheadings in a direction of rotation and intersecting at first throughnth corners defined by first through nth angles. First through nth basesare defined wherein the second through nth bases are located at thesecond through nth corners, respectively, and the first base is definedat a transition corner defined by a transition angle. The transitioncorner is defined at the intersection of the nth line segment and atransition line parallel to the first line segment and spaced toward theinterior of the region by one swath width. First through nth bisectorshaving headings toward the interior of the region at the first throughnth bases, respectively, are defined such that the first through nthbisectors bisect the transition angle and the second through nth angles,respectively. The spiral swath pattern is generated as a series ofconcentric swath lines to be driven by the work vehicle in the directionof rotation. Each one of the swath lines include first through nthlinear portions spaced apart at the swath width and correspond to thefirst through nth line segments, respectively. First through nth curvedportions are defined along a circle having a radius greater than orequal to the minimum turning radius tangent to consecutive linearportions and centered along the first through nth bisectors,respectively. The swath lines are generated as a function of at leastsome of: a) the boundary of the region; b) the minimum turning radius;c) the first through nth bisectors; and d) the swath width.

Because the swath lines of the spiral swath pattern are generated as afunction of the minimum turning radius, each curved portion, bydefinition, is within the turning capability of the vehicle. Unlikeprior art systems, computation of the radius of curvature of each curveand comparison of that radius to the minimum turning radius of thevehicle and possible modification of the swath line is unnecessary.

Subsequent swath lines are generated by defining first through nthlinear portions spaced one swath width from first through nth linearportions, respectively, of a previous swath line and defining firstthrough nth curved portions along circles having a radius greater thanor equal to the minimum turning radius tangent to consecutive linearportions of the previous swath line and centered along the first throughnth bisectors, respectively.

According to an aspect of the present invention, transition points fortransitioning between the linear portion and the curved portion for eachone of the swath lines are generated as a function of the first throughnth bases, the first through nth bisectors and the minimum turningradius.

According to another aspect of the present invention, first through nthskips for each one of the swath lines are identified as a function ofthe first through nth bases, the first through nth bisectors, theminimum turning radius, and the transition points for each one of theswath lines.

According to another embodiment of the present invention, additionalswath lines to be driven by the work vehicle are generated correspondingto the first through nth skips for each one of the swath lines.

According to a feature of the present invention, the swath pattern isgenerated by a control system of the work vehicle.

According to another feature of the present invention, the swath patternis generated remotely and communicated to the control system of the workvehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of this invention will be apparent upon consideration ofthe following detailed disclosure of the invention, especially whentaken in conjunction with the accompanying drawings wherein:

FIG. 1 is a top view of a representative work vehicle having animplement coupled thereto;

FIG. 2 is a top level representation of an automatic guidance systemincluding a swath generating apparatus according to the presentinvention;

FIG. 3 is a top view of a region of a field bounded by a convex polygonincluding a swath pattern generated according to the present invention;

FIG. 3 a is an enlarged view of a portion of the swath pattern of theregion of FIG. 3;

FIG. 3 b is the enlarged portion of the swath pattern of the region ofFIG. 3 including representative swath lines generated for the skips;

FIG. 4 is a top view of a region of a field bounded by a convex polygonincluding a swath line according to the present invention; and

FIG. 5 is a top level flow diagram of a method for generating a spiralswath pattern according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The swath generation methodologies described herein may find applicationin precision agriculture systems used to control crop sprayingoperations, harvesting operations, cultivation and plowing operations,planting and seeding operations, fertilizer application, or otheroperations where highly accurate positioning information is used inconjunction with defined patterns of swaths to control transit of avehicle over a land area. Such systems for precision locationdetermination are generally well known and are exemplified by thosedisclosed in U.S. Pat. Nos. 6,199,000 and 6,553,299, each entitled“Methods and Apparatus for Precision Agriculture Operations Using RealTime Kinematic Global Positioning Systems” which are incorporated hereinin their entirety by reference. Although the various methods will bedescribed with particular reference to GPS satellite-based systems, itshould be appreciated that the teachings are equally applicable toguidance systems using other methods to determine vehicle position.

A work vehicle, represented in FIG. 1 by a tractor 10, and an implement12 coupled thereto is of the type commonly used in agricultural andconstruction operations. Work vehicles are commonly equipped with aglobal positioning system (GPS), represented by vehicle positionreceiver 14, that determines position information used by a controlsystem 20 of an onboard computer 16 to simplify the task of drivingtractor 10. An operator may use an operator interface 18 to provideinput to control system 20. Included as part of control system 20 is anautomatic guidance system 22, a swath generating apparatus 24, and amemory device 26 as shown in FIG. 2. Typically swath generatingapparatus 24 generates generally parallel swath lines that, in theaggregate, define a swath pattern that covers the crop growing area ofthe field. Automatic guidance system 22 continually calculates a vehiclesteering heading by comparing vehicle position and directional headingto a desired swath line provided by swath generating apparatus 24, andsends the vehicle steering heading to a steering unit, which in turnactuates vehicle steering (i.e., steered wheels), thereby changing thevehicle heading in a well known manner. Tractor 10 may further includeother sensors which would also be communicatively coupled to controlsystem 20. Though shown as discreet devices within control system 20,the functions of automatic guidance control system 22, swath generatingapparatus 24, memory 26, and other portions of control system 20 caneasily be integrated into a single apparatus within the intent of thisinvention.

With reference to FIGS. 4 and 5, according to the invention, a method 30for generating a spiral swath pattern 34 to be driven by a work vehicle,such as tractor 10, over a convex polygon shaped region of a field 32 isdisclosed. As seen at step 100 of FIG. 5, method 30 includes determininga minimum turning radius 36 (see FIG. 4), such that the minimum turningradius defines the minimum radius of curvature of swath pattern 34. Atstep 102 swath width 38 (see FIGS. 3 and 4) is defined as a function ofa lateral extent of tractor 10 or implement 12.

Although method 30 is applicable to regions bounded by convex polygonshaving n sides, a representative swath pattern 35 generated by method 30for a region 33 having five sides (n=5) is shown in FIG. 3. Withreference to FIG. 4, method 30 is described for region 32 bounded by aconvex polygon having four sides.

According to step 104 a boundary 40 for region 32 is defined includingfirst through fourth (n=4) line segments 42, 44, 46, 48 having headingsin a direction of rotation depicted by arrow 50 and intersecting atfirst through fourth corners A, B, C, D defined by first through fourthangles 53, 54, 56, 58. According to step 106 of FIG. 5, first throughfourth bases A′, B′, C′, D′ having first through fourth base angles 52,54, 56, 58 are defined. Base A′ is a transition base located at atransition corner which defines a transition base angle 52 at theintersection of fourth line segment 48 and a transition line 60 parallelto first line segment 42 and spaced toward the interior of region 32 byone swath width 38.

According to step 110 of FIG. 5, first through fourth bisectors 62, 64,66, 68 having headings toward the interior of region 32 are defined atbases A′, B′, C′, D′, respectively. Bisectors 62, 64, 66, 68 bisectangles 52, 54, 56, 58, respectively.

At step 114 spiral swath pattern 34 is generated as a series ofconcentric swath lines 70 to be driven by tractor 10 in direction ofrotation 50. As can be seen in the example shown in FIG. 3 for n=5, eachone of the swath lines includes first through fifth linear portionsspaced apart at swath width 38 and corresponding to a line segmentbordering the region. First through fifth curved portions correspond tobases at second through fifth corners of the region and the transitionbase near the first corner. The swath lines of the spiral swath patternare generated as a function of at least some of the following: theboundary of the region, the minimum turning radius, the bisectors, andswath width.

Turning now to the example of FIG. 4, for partial representative swathline 70′, linear portions 72, 74, 76 correspond to line segments 42, 44,46, respectively. Curved portion 84 is defined along a circle 90 tangentto consecutive linear portions 72, 74 at transition points B1 and B2.Circle 90 is centered along bisector 64. Similarly, curved portion 86 isdefined along a circle 91 tangent to linear portions 74, 76 attransition points C1 and C2. Circle 91 is centered along bisector 66.Circles 90, 91 have radii greater than or equal to minimum turningradius 36, making curved portions 84, 86, by definition, include radiiof curvature greater than or equal to the minimum turning radius. Nocurved portions will be generated that the vehicle is unable to perform.To achieve this feature, when transition points B2 and C1 overlap,method 30 will no longer generate spiral swath lines because the radiusof curvature of a curved portion generated under this condition wouldhave a radius of curvature less than minimum turning radius 36. Forexample, if transition points B2 and C1 occurred in reverse orderrelative to direction of rotation 50, method 30 would not generatecurved portion 86 because the radius of curvature would be less than theminimum turning radius. This situation is depicted at area 94 of swathpattern 35 of FIG. 3 wherein no swath lines are generated. Unlike priorart methods, computation of the radius of curvature of each curve forcomparison to the minimum turning radius of the vehicle and possiblemodification of the swath line is unnecessary.

Subsequent swath lines are generated by defining first through fourthlinear portions spaced one swath width from first through fourth linearportions, respectively, of a previous swath line and defining firstthrough fourth curved portions along circles having a radius greaterthan or equal to the minimum turning radius tangent to consecutivelinear portions of the previous swath line and centered along the firstthrough fourth bisectors 62, 64, 66, 68, respectively.

According to an aspect of the present invention seen at step 112 of FIG.5, transition points, such as B1, B2, C1, and C2, for transitioningbetween the linear portion and the curved portion for each one of theswath lines are calculated as a function of first through fourth basesA′, B′, C′, D′, the first through fourth bisectors 62, 64, 66, 68, andthe minimum turning radius 36. As illustrated in FIG. 4, point B1identifies the transition point between linear portion 72 and curvedportion 84, and point B2 identifies the transition point between curvedportion 84 and linear portion 74. Similarly, C1 identifies thetransition point between linear portion 74 and curved portion 86, andpoint C2 identifies the transition point between curved portion 86 andlinear portion 76. The location of point B1, for example, can be foundas a function of bisector 64, minimum turning radius 36 and a base B′.

According to another aspect of the present invention seen at step 116 ofFIG. 5, first through fourth skips for each one of the swath lines areidentified as a function of as a function of first through fourth basesA′, B′, C′, D′, the first through fourth bisectors 62, 64, 66, 68, thetransition points, and the minimum turning radius 36. For example, skip98 shown cross hatched in FIG. 4 can be identified as a function of baseB′, bisector 64, minimum turning radius 36, and transition points B1 andB2.

According to another embodiment of the present invention, seen at step118 of FIG. 5, additional swath lines to be driven by tractor 10 aregenerated corresponding to the first through fourth skips for each oneof the swath lines. Example additional swath lines 92 are shown in FIG.3 b.

According to a feature of the present invention, the spiral swathpattern is generated by control system 20 of tractor 10.

According to another feature of the present invention, spiral swathpattern 34 is generated remotely and communicated to control system 20of tractor 10.

It will be understood that changes in the details, materials, steps, andarrangements of parts which have been described and illustrated toexplain the nature of the invention will occur to and may be made bythose skilled in the art upon a reading of this disclosure within theprinciples and scope of the invention. The foregoing descriptionillustrates the preferred embodiment of the invention; however,concepts, as based upon the description, may be employed in otherembodiments without departing from the scope of the invention.Accordingly, the following claims are intended to protect the inventionbroadly as well as in the specific form shown.

1. A method for generating a spiral swath pattern to be driven by a workvehicle over a convex polygon shaped region of a field, the methodcomprising the steps of: determining a minimum turning radius, such thatthe minimum turning radius defines the minimum radius of curvature ofthe swath pattern; defining a swath width as a function of a lateralextent of the work vehicle or an implement of the work vehicle; defininga boundary for the region including first through nth line segmentshaving headings in a direction of rotation and intersecting at firstthrough nth corners defined by first through nth angles; defining firstthrough nth bases, wherein the second through nth bases are located atthe second through nth corners, respectively, and the first base islocated at a transition corner defined by an intersection of the nthline segment and a transition line parallel to the first line segmentand spaced toward the interior of the region by one swath width;defining first through nth bisectors having headings toward the interiorof the region at the first through nth bases, respectively, such thatthe first through nth bisectors bisect the transition angle and thesecond through nth angles, respectively; generating the spiral swathpattern as a series of concentric swath lines to be driven by the workvehicle in the direction of rotation, each one of the swath linesincluding first through nth linear portions spaced apart at the swathwidth and corresponding to the first through nth line segments,respectively, and first through nth curved portions defined along acircle having a radius greater than or equal to the minimum turningradius tangent to consecutive linear portions and centered along thefirst through nth bisectors, respectively, the swath lines generated asa function of at least some of: a) the boundary of the region; b) theminimum turning radius; c) the first through nth bisectors; and d) theswath width.
 2. The method of claim 1, wherein subsequent swath linesare generated by defining first through nth linear portions spaced oneswath width from first through nth linear portions, respectively, of aprevious swath line and defining first through nth curved portions alongcircles having a radius greater than or equal to the minimum turningradius tangent to consecutive linear portions of the previous swath lineand centered along the first through nth bisectors, respectively.
 3. Themethod of claim 2, further comprising the steps of calculatingtransition points for transitioning between the linear portion and thecurved portion for each one of the swath lines as a function of thefirst through nth bases, the first through nth bisectors and the minimumturning radius.
 4. The method of claim 3, wherein first through nthskips for each one of the swath lines are identified as a function ofthe first through nth bases, the first through nth bisectors, theminimum turning radius, and the transition points for each one of theswath lines.
 5. The method of claim 4, further comprising the step ofgenerating additional swath lines to be driven by the work vehiclecorresponding to the first through nth skips for each one of the swathlines.
 6. The method of claim 1, wherein the swath pattern is generatedby a control system of the work vehicle.
 7. The method of claim 1,wherein the swath pattern is generated remotely and communicated to acontrol system of the work vehicle.
 8. A method for generating a spiralswath pattern including concentric swath lines to be driven by a workvehicle over a convex polygon shaped region of a field, the methodcomprising the steps of: determining a minimum turning radius, such thatthe minimum turning radius defines the minimum radius of curvature ofthe swath pattern; defining a swath width as a function of a lateralextent of the work vehicle or an implement of the work vehicle; defininga direction of rotation of the spiral swath pattern; defining a boundaryfor the region including first through nth line segments having headingsin the direction of rotation and intersecting at first through nthcorners defined by first through nth angles; defining first through nthbases having first through nth base angles as a function of the firstthrough nth line segments, the first through nth angles, and the swathwidth; defining first through nth bisectors at the first through nthbases, respectively, such that the first through nth bisectors bisectthe first through nth base angles, respectively; generating the spiralswath pattern as a series of swath lines to be driven by the workvehicle in the direction of rotation, each one of the swath linesincluding first through nth linear portions corresponding to the firstthrough nth line segments, respectively, and first through nth curvedportions corresponding to the first through nth bases, respectively, thefirst through nth curved portions defined along a circle centered alongeach one of the first through nth bisectors and tangent to consecutivelinear portions, the circle having a radius greater than or equal to theminimum turning radius, the swath lines generated as a function of atleast some of: a) the boundary of the region; b) the minimum turningradius; c) the first through nth bisectors; and d) the swath width. 9.The method of claim 1, wherein at least one base is defined at theintersection of one of the line segments and a transition line parallelto a consecutive line segment and spaced toward the interior of theregion by one swath width and generating the spiral swath patternincludes generating subsequent swath lines by defining subsequent firstthrough nth bases, defining first through nth linear portions spaced oneswath width from first through nth linear portions, respectively, of aprevious swath line and defining first through nth curved portions alongcircles having a radius greater than or equal to the minimum turningradius tangent to consecutive linear portions of the previous swath lineand centered along the first through nth bisectors, respectively as afunction of the first through nth bases of the previous swath line, thefirst through nth bisectors, the swath width, and the first through nthbase angles.
 10. The method of claim 9, further comprising the steps of:calculating transition points for transitioning between the linearportion and the curved portion for each one of the swath lines as afunction of the first through nth bases, the first through nth bisectorsand the minimum turning radius.
 11. The method of claim 10, whereinfirst through nth skips for each one of the swath lines are identifiedas a function of the first through nth bases, the first through nthbisectors, the minimum turning radius, and the transition points foreach one of the swath lines.
 12. The method of claim 11, furthercomprising the step of generating additional swath lines to be driven bythe work vehicle corresponding to the first through nth skips for eachone of the swath lines.
 13. The method of claim 8, wherein the swathpattern is generated by a control system of the work vehicle.
 14. Themethod of claim 8, wherein the swath pattern is generated remotely andcommunicated to a control system of the work vehicle.
 15. A method forgenerating a spiral swath pattern including a series of concentric swathlines to be driven by a work vehicle over a convex polygon shaped regionof a field, the method comprising the steps of: providing a vehicle withan implement; providing a control system having a processing capabilityand including an automatic guidance system, a swath generatingapparatus, and a memory device; providing a vehicle position receiverfor providing vehicle position information for the control system;providing an operator input device communicatively coupled to thecontrol system; communicating to the swath generating apparatus a set ofpredetermined parameters including a minimum turning radius, a swathwidth, and a definition of the field boundary including first throughnth line segments having headings in a defined direction of rotation andintersecting at first through nth corners defined by first through nthangles; defining within the swath generating apparatus a coordinatesystem for vehicle position; and generating within the swath generatingapparatus, a series of concentric swath lines to be driven by the workvehicle in the direction of rotation using the predetermined parameters,each one of the swath lines including first through nth linear portionscorresponding to the first through nth line segments, respectively, andfirst through nth curved portions corresponding to the first through nthcorners, respectively, the first through nth linear portions beinggenerally parallel to and spaced apart by one swath width from the firstthrough nth linear portions of adjacent swath lines, respectively, thefirst through nth curved portions defined along a circle tangent toconsecutive linear portions, the circle having a radius greater than orequal to the minimum turning radius, each one of the swath linesbeginning at an end point of the previous swath line wherein theinterconnected swath lines form a spiral swath pattern.
 16. The methodof claim 15, further comprising the steps of: defining first through nthbases having first through nth base angles as a function of the swathwidth, the first through nth corners, and the first through nth angles,respectively; and generating subsequent swath lines as a function of thefirst through nth bases of the previous swath line, the swath width, andthe first through nth base angles.
 17. The method of claim 16, furthercomprising the steps of: calculating transition points for transitioningbetween the linear portion and the curved portion for each one of theswath lines as a function of the first through nth bases, the firstthrough nth base angles, and the minimum turning radius.
 18. The methodof claim 17, wherein first through nth skips for each one of the swathlines are identified as a function of the first through nth bases, thefirst through nth base angles, the minimum turning radius, and thetransition points for each one of the swath lines.
 19. The method ofclaim 4, further comprising the step of generating additional swathlines to be driven by the work vehicle corresponding to the firstthrough nth skips for each one of the swath lines.
 20. The method ofclaim 15, wherein the swath pattern is generated remotely from the workvehicle.